Can't claim for child - any support?

[Fundingissues]

Hi, I'm a regular poster but name changed as this will 100% be outing to anyone who knows us, I'm posting on behalf of my mum/sister. My sister is 17, 18 at the end of July. I live with my own DC so not included in the finances here. Straight from high school my sister went to the army foundation college Harrogate and was paid as a junior soldier. She passed everything and went to a base as a soldier but unfortunately she has now been medically discharged. My mum has other children under 16 and claims UC/carers allowance, she doesn't work as she is a carer for my disabled grandfather. My sister is back living at home with my mum since leaving the army and has a confirmed place at college for a level 3 qualification starting in September, however my mum has been advised that until then she cannot add her back on to claim any money for her (child benefit, universal credit child element etc) even though she was still able to claim it between finishing high school and starting AFC in September, and would've been able to claim it between finishing high school and my sister going to college for this course had it been straight away (as many do). My sister had savings but has used them as she's been paying money to my mum to help since she moved back and also whilst she was still on base as during covid she had to stay with my mum a lot so helped with bills - obviously she is still under 18 so can't claim anything in her own right either. Does anyone know of anything either of them can do to get some financial support as my sister is basically living on nothing at the moment - she has been and still is consistently applying for any and every part time job but either she doesn't have the experience or they don't even get back to her, and before she got her confirmed college course was looking at full time jobs even residentials etc but obviously now she won't be able to do that for 2 months and then just leave, if they even started straight away. Can anyone help? TIA

i think there are certain circumstances where a 17 year old can claim Uc if they have no parental support, but not entirely sure of the criteria.
I'm not sure your mum would be able to add her to her Uc claim once she is 18 anyway ?
How long was your sister in the army for and did she pay NI contributions ? she probably will be short on NI contributions to claim new style JSA but worth checking on the GOV. uk site via government gateway. Unfortunately I think this could be one of those cases that falls between the gaps.

I have just looked at the guidelines and the only way around it as far as I can see is maybe if she became a carer for her granddad (instead of your mum) and could then claim UC as a carer. Obviously your mum would lose carers element off her Uc but overall the household would gain significantly. Obviously this may not be feasible ! Perhaps speak to CAB to see if they can advise anything else.
www.entitledto.co.uk/help/claims-by-16-and-17-year-olds

Thanks. Definitely able to re add her once she is back in education as you can claim up until child is 19, it's just that as my sister isn't in education or training at the moment (even though she has a guaranteed place) because there was a break in the claim she can't claim it over the period in between. No unfortunately not really feasible as my mum has to do absolutely everything for my grandad including driving to and from hospital every other day or so, sister doesn't drive, couldn't even switch it over for financial reasons and still have my mum do that part of it as then my mum would have to be working/looking for work and do all that as well which is why she claims carers in the first place as it would be too much.

I'll ask about the NI, she has been in since sept 2019. If my sister wasn't going back into education no she wouldn't be able to add her back to the claim, so think that's where the confusion is.